Corn milling processes are employed to separate corn into the various components of the corn kernel. Such processes are divided into two broad categories known as wet-milling processes and dry-milling processes. In the wet-milling processes, the corn is first steeped in an aqueous solution to soften the kernel. Dry-milling processes, on the other hand, use dry or slightly moistened grain which has not been subjected to the steeping operation.
The general purpose of corn dry-milling processes is to separate the corn kernel into germ, endosperm, and fiber fractions. These processes vary somewhat depending on the nature of the corn, the ratio of products desired, and various consumer preferences. Generally, the whole corn kernels are first cleaned to remove chaff and other extraneous material. The cleaned grain is then tempered with water or steam which tends to increase the water level in the various portions of the corn kernel. Next, the tempered grain is passed through a degerminating mill to release the fiber (hull) from the germ and endosperm.
In the usual corn dry-milling process, the discharge from the degerminating mill comprising corn fiber, germ, and endosperm is sifted into fractions according to particle size. The sifted fractions are subjected to a series of air aspiration steps to separate the fiber from the germ and endosperm. The mixture of germ and endosperm then undergoes further separation and purification treatments. As noted, the conventional dry-milling process requires aspirators to separate the fiber from the other components. The cost of this equipment, together with related air-handling equipment and dust collectors, add to the cost of this separation which also has a fairly high energy requirement.